The invention relates generally to apparatus for preparing on a continuous basis, mixtures of a plurality of constituent materials and, more specifically, to apparatus for continuous flow weighing of a dry flowable material for addition in a desired proportion to a mixture.
Mixtures or rations are typically made by mixing multiple ingredients by either the technique of batching by volume or weight or by the technique of continuous volumetric proportioning. Batching by volume or weight requires use of a batch mixer. Each ingredient is loaded into the mixer sequentially, the amount of each ingredient to be added is measured either by volume or, more accurately, by weight. After all of the ingredients have been loaded into the mixer, the mixer is operated until a homogeneous mixture of the ingredients is obtained.
The batching method provides for accurate measuring of ingredients and can be automated to load ingredients according to predefined recipes. Its disadvantages include the time required for sequential loading of ingredients, inaccuracy if ingredients are measured by volume, and operator error as is often the case with microingredients (i.e., ingredients added in very small proportional amounts).
The volumetric proportioning method does not require a mixer. Each ingredient flows simultaneously through separate augers into a common gathering auger. The flow rate of each ingredient is controlled by controlling the speed of the individual ingredient augers. Volumetric proportioning can be accomplished with a simple, compact system that does not require a mixer and which is potentially inexpensive to purchase and maintain. This method, however, has relatively low accuracy, being dependent on material flow characteristics and constancy of material density. Microingredients must typically be preblended into another ingredient to obtain the necessary minimum flow rates of the augers. Further, volumetric flow proportioning requires a separate metering auger for each ingredient.